1. Field of the Invention
The present invention relates to a process for the production of (+)-2-amino-1-butanol. More particularly, the present invention relates to a process for producing (+)-2-amino-1-butanol which comprises esterifying L-2-aminobutyric acid obtained by the optical resolution of DL-2-aminobutyric acid and reducing the resulting L-2-aminobutyric acid ester.
2. Description of the Prior Art
(+)-2-Amino-1-butanol is an important intermediate for producing (+)-2,2'-(ethylenediimino)di-1-butanol (generally called Ethambutol) which has a remarkable antitubercular action, and only the (.+-.)-2-amino-1-butanol is required (see Wilkinson R. G. et al, J. Am. Chem. Soc. 83, 2212 (1961)).
Also, it is known that racemic form or meso form -(ethylenediimino)di--(ethylenediimino) 1-butanol produces strong undesirable side effects on the eyes (see, for example, Arch. Ophtal. 67, 566 (1962) and Ibid, 68, 718 (1962)). Thus, an extremely high optical purity is required for (+)-2-amino-1-butanol.
Hitherto, (+)-2-amino-1-butanol has been produced by forming an intermediate of 2-nitrobutanol from 1-nitropropane as a starting material, synthesizing (.+-.)-2-amino-1-butanol from the intermediate, and optically resolving the (.+-.)-2-amino-1-butanol. The yields obtained have averaged as low as about 10%. Furthermore, (-)-2-aminobutanol simultaneously produced is quite difficult to be racemized and thus the hitherto used method is economically disadvantageous.
In the course of investigations on a process for producing (+)-2-amino-1-butanol which is different from the hitherto used method, attention was directed toward the optical isomers produced by the optical resolution of DL-2-aminobutyric acid and in detail toward a reducing method and reducing agent for the ester of the DL-2-aminobutyric acid. As a result, it has been found that (+)-2-amino-1-butanol can be produced from L-2-aminobutyric acid and an economical synthesis of (+)-2-amino-1-butanol has been established.